Fractures of the tibia are traditionally treated with either (i) an intramedullary rod (sometimes referred to as an intramedullary nail) which is positioned in the intramedullary canal of the tibia, or (ii) a plate applied to the side of the tibia and fixed in place with screws set into the tibia. The choice of using an intramedullary rod or a plate is generally based on the location and complexity of the fracture.
As noted above, the intramedullary rod is placed in the intramedullary canal of the tibia and typically provides excellent mechanical stability for the bone. Among other things, the intramedullary rod exhibits good weight-sharing properties. However, the use of an intramedullary rod also involves a more complex surgical procedure and higher cost.
Plates are generally simpler to deploy and less expensive than intramedullary rods. However, it can sometimes be difficult to achieve proper support for the fracture site with plates upon the application of weight.
Intramedullary rods have evolved over time.
The first generation of intramedullary rods essentially involved inserting a solid rod down the intramedullary canal of the bone. This type of intramedullary rod is relatively primitive and only grossly re-aligns the bone. The first generation of intramedullary rods does not control motion at the fracture line in any specific plane.
The second generation of intramedullary rods saw the introduction of the so-called interlocking intramedullary rod. The interlocking intramedullary rod allows for compression of the bone at the fracture site by allowing axial compression of the fracture. This axial compression of the fracture is achieved through the use of lag screws which pass through the bone (e.g., in the medial-to-lateral direction, posterior-to-anterior direction, etc.), across the intramedullary rod and back into the bone.
However, with current interlocking intramedullary rods, the surgeon cannot easily adjust the disposition of one of the bone fragments (e.g., the proximal bone fragment) relative to the other of the bone fragments (e.g., the distal bone fragment). This makes it challenging for the surgeon to align the two bone fragments relative to one another in an optimal manner. More particularly, with current interlocking intramedullary rods, the surgeon must first adjust the disposition of one of the bone fragments (e.g., the proximal bone fragment) relative to the other of the bone fragments (e.g., the distal bone fragment), then temporarily hold the two bone fragments in the desired alignment while the interlocking intramedullary rod is inserted into the intramedullary canal, and finally insert one or more lag screws through each of the bone fragments and through the interlocking intramedullary rod so as to secure the bone fragments to the interlocking intramedullary rod. As this occurs, one of the bone fragments may become misaligned relative to the other of the bone fragments, so that it is secured to the interlocking intramedullary rod in a non-optimal manner.
In view of the foregoing, it is an object of the present invention to provide a novel interlocking intramedullary rod assembly which allows the surgeon to (i) secure a first bone fragment of a fractured bone (e.g., a distal bone fragment) to the interlocking intramedullary rod assembly in a fixed position, (ii) secure a second bone fragment of the fractured bone (e.g., a proximal bone fragment) to the interlocking intramedullary rod assembly in an adjustable manner, and (iii) thereafter selectively pivot the second bone fragment (e.g., the proximal bone fragment) relative to the first bone fragment (e.g., the distal bone fragment) so as to secure the two bone fragments in position relative to one another with the desired orientation and/or with the desired degree of compression.